In recent years less invasive surgery (e.g., laparoscopic surgery) has become the standard method for performing several common procedures, e.g. a cholecystectomy. These procedures are generally performed by inserting a trocar casing through a body cavity wall to gain access to a body cavity or region. The trocar casing is used as an access port for the introduction of instruments to provide visualization and to operate upon organs within the cavity.
In order to penetrate the body cavity wall through which the trocar casing is to pass, an obturator is fitted within the tube of the trocar. Obturators typically comprise a main shank with a solid metal tip having three sharp edges at its distal end. The tip of the obturator is manually forced through the body wall to create an opening through which the trocar casing may pass. Typically, the surgeon must apply considerable force to the proximal end of the obturator to cause the tip to penetrate the soft body tissue, i.e. skin-fat-muscle-peritoneal layers of the body cavity wall. Once the wall is penetrated, however, there is an abrupt drop in penetration resistance. Typically, the surgeon may not be able to respond fast enough to avoid over-insertion, with the result that the sharp obturator tip may be thrust into the body cavity, potentially causing injury to the organs or vessels contained therein.
In addition to the inherent danger of damaging tissue within a body cavity as a result of over-insertion, current obturator structures may cause significant bleeding in a body cavity wall upon penetration. This bleeding can cloud the area to be operated upon, and thereby reduce the surgeon's view through visualization optics carried within the trocar casing. Accordingly, once the body cavity wall has been penetrated by the obturator tip, the resulting bleeding must be stopped, or the blood cleared away before the operation can be safely performed. These steps may prolong the surgical procedure and result in increased patient discomfort.
In an attempt to address the problem associated with obturator over-insertion, the prior art has proposed several solutions. For example, Green, U.S. Pat. No. 5,116,353 teaches a safety trocar structure wherein the cutting tip of the obturator is withdrawn into the cannula of the trocar casing in response to a counterforce being removed from the the cutting tip. The cutting tip is maintained in an exposed position as the surgeon forces the tip against the body cavity wall; however, when the tip penetrates the body cavity wall it is automatically withdrawn into the cannula under the force of a spring.
Even in devices such as taught by Green, inadvertent patient injury can still occur when the force to penetrate the body wall suddenly drops upon entry into the cavity. Typically, a surgeon is unable to predict and accurately control the force required to penetrate the wall. If too great a force is asserted, a device such as that taught by Green may not react fast enough to withdraw the sharp tip of the obturator into the trocar cannula. In addition, while the tip may retract, the entire trocar tube may be overinserted potentially injuring the patient. Also, the possibility of mechanical failure caused by repeated use presents an inherent potential for injury from the sharp edges of the obturator tip.
In addition to the potential for injury caused by overinsertion that persists in prior art obturator structures, the prior art has failed to address the problems associated with the bleeding of the body cavity wall upon penetration. As a result, existing obturator devices continue to suffer from the disadvantages cited above, thereby decreasing the overall safety, efficiency and patient comfort in commonly performed less invasive surgical procedures.